Root infection of canker pathogens, Fusarium circinatum and Diplodia sapinea, in asymptomatic trees in Pinus radiata and Pinus pinaster plantations

[EN] The existence of a latent stage within host tissue of the pine pathogens Fusarium circinatum and Diplodia sapinea, the causal agents of pitch canker and shoot blight disease respectively, has previously been cited. However, studies on this cryptic phase in each disease lifecycle has only been focused on the host aerial parts but not on the roots. Therefore, our objective was to analyze the presence of both pathogens in roots of non-symptomatic mature trees in plantations where the pathogens are known to be causing canker symptoms. For that, we sampled roots from ten non-symptomatic and ten symptomatic trees in three Pinus radiata and one Pinus pinaster plantations in Basque Country, Spain. Both pathogens were isolated from roots of non-symptomatic trees in a higher frequency than from roots of symptomatic trees, 23.3% and 6.6% respectively for D. sapinea and 16.6% and 3.3% respectively for F. circinatum. Neither pathogens was detected in the P. pinaster plantation. The two pathogens were never isolated from the same tree. A high molecular variability was observed for D. sapinea isolates with six different haplotypes and two mating types for the eleven characterized isolates, but only one haplotype and mating type was found for F. circinatum, with all isolates of both fungi being proved pathogenic. These results evidence the importance root infection may have in the disease lifecycle and, therefore, disease management. We acknowledge Maria Teresa Morales Clemente for her excellent technical assistance. Laura Hernandez-Escribano was supported by a fellowship from INIA (FPI-INIA). Financial support for this research was provided by project RTA2013-00048-C03-01, RTA2017-00063-C04-01 and C04-03 (National Progamme I + D + I, INIA, Spain) and the Project Healthy Forest LIFE14 ENV/ES/000179. This article is-based upon work from COST Action FP1406, Pine pitch canker-strategies for management of Gibberella circinata in greenhouses and forests (PINESTRENGTH), supported by COST (European Cooperation in Science and Technology). Hernandez-Escribano, L.; Iturritxa, E.; Aragonés, A.; Mesanza, N.; Berbegal Martinez, M.; Raposo, R.; Elvira-Recuenco, M. (2018). Root infection of canker pathogens, Fusarium circinatum and Diplodia sapinea, in asymptomatic trees in Pinus radiata and Pinus pinaster plantations. Forests. 9(3):1-15. https://doi.org/10.3390/f9030128 Nirenberg, H. I., & O’Donnell, K. (1998). New Fusarium Species and Combinations within the Gibberella fujikuroi